New concepts are proposed for controlling biomimetic polyene cyclizations so that they may be employed for efficient total asymmetric syntheses of some new medicinals as well as ones of established importance, with the aim of making the latter more readily available. An immediate target of highest priority is Spironolactone and analogs for treatment of hypertension. Other targets include 19-nor-steroidal oral contraceptives and corticoids. When acetylenic groups are used as terminators of such cyclizations, the process is often not highly stereoselective, whereas olefinic terminators promise to give very high stereoselectivity. Part 1 of this proposal is concerned with the development of effective olefinic terminators for steroid synthesis via polyene cyclization strategy. Part II envisages an approach to steroid total synthesis in which an oxy substituent at pro-C-7 (rendering this center chiral) in the cyclization substrate serves not only to promote asymmetric cyclizations, but also to generate 7-substituted steroids, e.g., Spironalactone. The approach promises to be adaptable to asymmetric synthesis also of 19-nor steroids. The effect of even more remote chiral centers (e.g., at pro-C-14) will be examined in the hope of shedding light on the mechanism of polyene cyclizations, i.e., the amount of coiling in the transition state. Attempts to produce 19-nor steroid systems via polyene cyclizations have resulted in the formation of abnormal products arising from backbone rearrangements via hydride shifts. Part II involves a rearrangements during polyene cyclizations. Part IV. Template-controlled cyclizations. This part is aimed at determining if cyclization of polyene substrates, which are linked to chiral templates, will proceed with efficiency and with asymmetric induction, thus mimicing in principle the enzymatic process.